This invention relates to spiral wound abrasive belts, and methods and apparatus for making the same.
Endless coated abrasive articles, such as belts, sleeves, tubes and the like, are used in a variety of abrading operations, especially in the woodworking and metal finishing industries. These operations require that the articles be made and supplied by the coated abrasive manufacturer in a large variety of widths and circumferences.
Standard belt forming techniques provide coated abrasive belts in widths equal to the widths of the coated abrasive materials from which they are formed. Typically, a piece of coated abrasive material, equal in width to the desired belt width, is cut at a suitable angle across its width. The piece of material is then measured to a length equal to the desired belt circumference plus an allowance for forming a lap joint, if desired. A second cut across the width is then made at the same angle as the first cut. An adhesive composition is then applied to one or both ends and the ends are joined by overlapping, causing the ends to adhere to one another by means well known to those skilled in the art.
Alternatively, the piece of coated abrasive material may be cut to a length without an allowance for a lap joint. In this situation, the ends of the material are butted and joined to one another with an overlapping reinforcing flexible patch suitably adhered to the backside of the two ends of the material.
Another alternative method for making a coated abrasive belt is disclosed in European Patent Application. No. 0497451, published Aug. 5, 1992, wherein the method provides a coated abrasive belt that includes an abrasive layer bonded to a flexible backing material, which in turn includes a flexible support and a layer of hot-melt adhesive. A butt joint is formed at the ends of a strip of the material with heat and pressure added to cause the hot-melt adhesive to flow across the joint.
Coated abrasive belts in widths greater than the width of the coated abrasive material have been produced by a number of methods. One such method involves piecing together segments of coated abrasive material to form wide, multi-jointed sectional belts that cover a broad range of belt widths and belt circumferences. These belts, however, have the drawback of increased cost due to the multiple piecing and joining processes required to fabricate the belts. In addition, multiple joints increase the potential for problems due to weakening of the belt at the joints, as well as process control and quality issues.
Another method of forming an endless coated abrasive belt that has a width greater than the width of coated abrasive material from which it was made involves spiral winding of material. A conventional method for making such xe2x80x9cspiral woundxe2x80x9d belts involves winding an inner liner spirally on a mandrel having an outer circumference equal to the inside circumference of the desired abrasive belt, applying an adhesive to the outer surface of the inner liner, and winding spirally over the adhesive layer a strip of coated abrasive material. Such a method is widely used for the fabrication of belts in smaller sizes, up to, for example, 6 inches in diameter or 19 inches in circumference.
Another such method involves spiral winding narrow strips of coated abrasive material having scarfed (or angle cut) edges that overlap and are adhered using conventional techniques. Alternatively, the edges of a piece of wider coated abrasive material may be formed to abut when wound spirally within a revolvable drum. Subsequently, a resinous coating material is applied to the inner periphery of the belt which then spreads, as the drum revolves, to form a continuous layer of resinous coating that joins the belt material together. Yet another method involves spiral winding about a mandrel a coated abrasive material with abutting edges that has a flexible backing material including a layer of hot-melt adhesive. The spiral wound material is then heated to cause the hot-melt adhesive to flow across the abutted edges resulting in a continuous layer that secures the edges together.
There are numerous shortfalls in the methods described above. Use of a fixed mandrel or drum limits the belts formed on such mandrel or drum to a single diameter. Use of thinner material with these methods makes it difficult to line up the seams and traditional cloth abrasive media may have baggy edges that form puckers or uneven seams in the belt, both of which can cause processing and belt performance problems later on. These methods are usable to form belts one at a time, making them inefficient, less productive and more expensive. In addition, the types of abrasive materials usable with these methods are not typically sufficiently reinforced, such that the resulting abrasive belts tend to delaminate at the seams or during use over time.
An ongoing need exists for spiral wound abrasive belts that are produced in a faster, cheaper and more efficient manner, and in a variety of sizes. Such spiral wound belts that take advantage of abrasive media constructions that produce stronger and more durable abrasive articles are also desirable.
The present invention is a spiral wound abrasive belt formed from an abrasive media including a plurality of webs, and a method and apparatus for constructing the same. The webs of the abrasive media may include coated abrasives joined by splicing media or other suitable joining material. Alternatively, the webs may include individual single or multiple layers that form a coated abrasive simultaneously along with the spiral belt without the use of additional joining material.
In one embodiment, the abrasive media may be draped over a fixed hub at an angle to form the spiral belt while abutting the inner edge of the spirally wrapped web with the outer edge of the succeeding wrap of web. Heat and pressure may be applied to the joined edges to form a strong bond along the spiral seam. In another embodiment, the webs forming the abrasive media may be introduced at an angle and draped over a fixed hub. The abrasive media may then be passed around an adjustable hub that provides tension in the spiral belt while allowing for different circumferentially sized belts. Continuous feeding of the input abrasive media or webs will result in a spiral belt of ever increasing width that may subsequently be slit to a desired width. Optionally, an outermost web positioning system, including sensors, a controller and a web positioning mechanism may be provided to minimize gaps or overlaps along the spiral seam.